Servosystem altitude adjustment for bomb sight



Oct- 24, 1961 u. c. s. DILKS 3,005,938

SERVOSYSTEM ALTITUDE ADJUSTMENT FOR BOMB SIGHT Original Filed Jan. 9, 1946 s Sheets-Sheet 1" BOMBSIGHT ALTITUDE KNOB SERVO MOTOR FIG. I

SERVO I CONTROLLER INVENTOR USELMA 6. 5. OIL/(.9

ATTORNEY u. c. s. DILKS 3,005,938

SERVOSYSTEM ALTITUDE ADJUSTMENT FOR BOMB SIGHT Oct. 24, 1961 3 SheetsSheet 2 Original Filed Jan.

ATTORNEY ALTITUDE //v FEET Oct. 24, 1961 u. c. s. DILKS 3,

SERVOSYSTEM ALTITUDE ADJUSTMENT FOR BOMB SIGi-IT Original Filed Jan. 9, 1946 3 Sheets-Sheet 3 ALTITUDE IN FEET INVENTOR USE LMA 6! S. DILKS- BY ,fiQm

ATTORNEY Fla. 3

i r v United States Patent Ofice 3,005,938 SERVOSYSTEM ALTITUDE ADJUSTMENT FOR BOMB SIGHT Us'elma Clarke Smith Dilks, Narbeth, Pa., assignor to 5 the United States of America as represented by the Secretary of the Navy Original application Jan. 9, 1946, Ser. No. 640,113. D1-

vided and this application Feb. 9, 1954, Ser. No. 409,281

6 Claims. (Cl. 318-48) 3,005,938 I Patented'Oct. 24, 1961 in block form, for use in explaining the general principles 10 nal having a magnitude functionally related to altitude,

The present invention relates to bomb sights of the type in which an adjustment member is set in accordance with the bombing altitude or some function of altitude in order to solve the range phase of the bombing problem.

More particularly the invention relates to an improved electrical control arrangement for automatically setting the altitude adjustment member"of seeh bcmb sightsfii This application is a division of the application Serial No. 640,113, filed January 9, 1946, with the same title and assigned to the same assignee.

The present invention is of particular utility in controlling the altitude setting of a low-altitude bomb sight.

The present invention is of general utility in furnish ing to any conventional type of bomb sight a datum signal' representative of altitude or a desired function of altitude. The expressionsaltitude adjustment member, altitude adjustment kno altitude adjustment dial, and the like, as used in specification and in the appended claims, are intended to comprehend any element of a bomb sight which is set in accordance with altitude or a function of altitude in order to place the sight in condition for solving the range problem. Neglecting for the moment all factors aifecting the trajectory of a bomb other than gravity. and the closing speed between bombing aircraft and target, and assuming a proper collision course for the craft, it will be seen that the range of the bomb (amount of forward travel measured on the earths surface from a point vertically below the craft at the instant of release to the point of impact) is a function of closing speed and the time of flight of the bomb. The

bomb sight solves the range porblem by finding the proper dropping angle (the angle between the vertical through the bomb sight and the line of sight to the target at the proper instant of bomb release) and furnishes output data which permit the bomb to. be dropped whenth dropping angle and range are correct. Since time of flight is a function of altitude, it will be seen that altitude is one of the necessary inputs to a low-level bomb sight, and that altitude or some function thereof is a necessary input to any bomb sight. The altitude adjustment is ge 5 frequency signals.

a bombsight 12 having an altitude adjustmentmember 13, and means controlled by the electrical signal produced by the altimeter for setting the adjustment member, the

last-mentioned 'nfeansfimmprisingarserve'eenaeller and motor arrangement indicated generally by the numeral 14. It will be understood that units 111, 1'2 and 14 are adapted to be installed in and carried by a bombing aircraft.

Altimeter 11 is of a conventional type and its construction and overall operation are well known to those skilled in the art. Briefly, however, it comprises an audio-frequency oscillator 15 for generating sinusoidal modulating signals, these signals being applied to the voice coil of a frequency modulator (not shown). Such a modulator preferably comprised a grounded diaphragm and a silvered ceramic head plate, forming dual modulating capacitors. The diaphragm is driven by a voice coil assembled in a permanent-magnet loud-speaker typestructure. The output circuit of oscillator 15 is coupled to the input circuit of a frequency-modulation transmitter 16. The transmitter includes a push-pull radio-frequency oscillator (not shown) ofthe variable plate-circuit reactance type for generating radio frequency signals. Also included in the transmitter is the above-mentioned frequency modulator (not shown) 1 for varying the reactance of the transmitter plate circuits in accordance with the modulating signals, whereby the transmitter produces sinusoidally' frequency-modulated output signals. The output circuit of the transmitter is coupled to an au- 40 tenna 17, which propagates the transmitter output signal energy to the earth as well as directly to the receiving antenna hereinbelow described.

The altimeter also includes a receiving antenna 18 for intercepting both the frequency-modulated signals directly propagated from antenna 17 and the frequency-modulatediignals redectedmremthe *6fiFiii. Pi%% f$$i" ne m tenna is coupled to the input circuit of a balanced detector 19, which mixes the frequency-modulated direct and reflected signals thereby to produce heterodyne beat- The beat-frequency signals have an erally made by turning a dial or knob to a desired position.

A device for automatically applying altitude'data frem a barometric altimeter to a bomb sight is disclosed in the copending patent application of Carl A. Norden, Serial No. 574,593, filed in the US. Patent Office on January 25 1945, entitled Bomb Sight, and assigned to the same assignee as the present. application and invention now Patent No. 2,703,932.

It is an object of the present invention to provide an improved electromechanical arrangement for automatically applying altitude data from an electronic altimete to a bomb sight. I

It is also an object of the invention to provide an improved servo-motor control and relay arrangement.

For a better understanding of the present invention, to get-her with other and further objects thereof, reference is made to the following specification and the claims appended thereto and to the accompanying drawings in which:

FIG. 1 comprises an equivalent circuit diagram, partly instaulanecnvfrequenfi fieportienalae the difference between the instantaneous frequencies of the direct and reflected signals and have an average frequency proporportional to the altitude of the aircraft above the earth. The output circuit of detector 19 is coupled to the input circuit of an audio-frequency amplifier 20, provided for the purpose of amplifying the beat-frequency detector output signals. Coupled to the output circuit of the amplifier is a limiter 21"f0r converting the amplified signals into limited signals having a frequency proportional to altitude and comprising square 'waves of substantially the same amplitude. The limiter modifies and shapes the amplifier 20 output signals in such a manner as to eliminate amplitude variations and to insure uniformity of amplitude and pulse duration. The result is that the pulserepetition frequency constitutes the only variable and it may be measured. The limiter is followed by a counting and integrating circuit, included in an altitude indicator and amplifier unit 23. Unit 23 converts the pulse signals applied thereto into a direct-current output signal having a magnitude approximately proportional to the frequency tiiinal to the average cf'that' dirieren'ceand thereforepro of the limited signals and therefore proportional to altitude.

Although it is not intended to limit the invention to any particular circuit dimensions or any specific components, certain circuit parameters found to be practicable in one successful embodiment of the invention are furnishcd for purposes of illustration in the detailed descrip tion of the ptior-art altitude indicator and amplifier unit 23 and the detailed description of the servo controller and motor 14 provided in accordance with the invention.

Specifically the limiter output signals are applied to two counter capacitors 25 (25 micromicrofarads) and 26 (62 micromicrofarads), capacitor 25 being variable. Assuming positive polarity for the limiter output pulses, the operation of unit 23 during one pulse cycle'is considered. At the instant of application of the leading-edge portion of a pulse to condensers 25-26, anode 27 becomes sufficiently positive with respect to cathode 23 of double-diode tube 29 (121-16) to render diode 27-428 conductive. Electrons accumulate on the plates of condensers 25a26 electrically adjacent to diode 27-28 as the condensers gain an increment of charge, the path of electron flow including the grounded terminal of limiter 21, ground, portion 35 of variable resistor 36 (30,000 ohms), load resistor 34 (1 megohm), cathode 28 and anode 27, the circuit being completed by capacitors 25-..26 and a connection to the high-potential terminal of the limiter. At the end of the increment of charge anode 27 is at a sufliciently low potential with respect to cathode 28 to render diode 27-28 nonconductive. At the termination of the pulse the drop in applied voltage leaves the diode side of condensers 2 -25 at a negative potential appropriate to this increment of charge. Diode 274-28 cannot conduct elect-rons'away from conductors 25=-26 at this time but diode 31-38 becomes conductive and condensers 25-26 discharge, the accumulated electrons flowing through cathode 37 and anode 38 to ground, some going through resistor '34} (50.00 ohms), altitude indicator 31 (a 1.5-6.5 direct-current milliammeter, calibrated in terms of altitude in feet), and ground to the grounded terminal of limiter 21, This sequence is repeated, the countercapacitors being charged on each positive pulse and discharging on each interval between pulses or half cycle of the signal from limiter 21. It is apparent that, Since a certain amount of current flows through resistors 34-35 each time a pulse cycle is repeated, an average current which increases as the pulse recurrence frequency increases and decreases as the frequency decreases flows therein. The resultant potential drop in resistors 34-35 is such as to charge condenser 33 (0.125 microfarad) with positive polarity. Condenser 33 stabilizes the average positive direct-current voltage developed across load resistor 34 and resistor 35, since it loses a part of its charge during that portion of the cycle when capacitors 25 and 26 are discharged, the electrons from its grounded plates flowing through resistors 35 and 34 to its plates connected to cathode 28, thereby tending to maintain current flow in those resistors in the interval between successive charges of capacitors 25 and 26. Condenser 33 has an average charge which increases as the recurrence frequency of the applied pulses increases and decreases as frequency decreases.

This voltage appearing across resistors 34 and 35 is proportional to the recurrence frequency of the pulse signals from limiter 21 and therefore to altitude. The amplitude of this voltage is adjusted for calibration purposes by means, of the variable altitude indicator counter capacitor 25.

The function of the altitude indicator amplifier is to supply to the altitude indicator meter 31 a current which is controlled by the voltage developed by the altitude indicator counter across load resistor 34 and resistor 35. The direct current potential developed across resistors 34 and 35 is applied to the amplifier stage through a filter, consisting of a series resistor 32 (1 megohm) and a shunt capacitor 39 (0.05 microfarad) and through resistor 40 (1000 ohms) to the control electrode of a pentode amplifier tube 41 (12SH7), operated as a direct-current power amplifier. The suppressor grid of this tube is connected to the cathode and the anode and screen grid are coupled to appropriate sources of potential (not shown), indicated as +S.G. and+P, respectively (150 volts and 250 volts, respectively). The load impedance of this type of direct-current amplifier appears in the cathode circuit and consists of the series combination of meter 31 and resistors 42 (5000 ohms) and 30, resistor 42 being connected to cathode 43. The altitude indicator zero adjustment potentiometer 36 is provided for calibration purposes. This control provides a small adjustable positive bias in series with resistor 34 to the control electrode of tube 41. It will be seen that the diode section 37, 38 returns to the junction of resistors '30 and 42, thereby providing a positive voltage to the anode of this diode. This expedient improves the overall linearity of the altitude indicator system since it provides a path parallel to that of elements 30, 31 for the discharge of the counter capacitors 25-26, some of the discharged electrons flowing from anode 38 through resistor 42, tube 41 and source +1? to ground, thus aiding plate current flow in tube 41. In order to provide the positive bias for the control grid of tube 41, resistor 36 is connected in series with resistor 45 (270,000 ohms) and the latter is connected, to an appropriate potential source (not shown) indicated as +G (150 volts).

Referring now specifically to FIG. 3 of the drawing, there is illustrated a curve showing output voltages between the junction of resistors 30 and 42 and ground plotted as ordinates against altitudes as abscissae. This curve represents results empirically obtained with an al' timeter having the parameters hereinabove suggested and incorporated in one successful embodiment of. the present invention.

It has been seen that tube 41 is connected as a cathode follower. It therefore acts as a power amplifier, without voltage amplification, and causes sufficient current flow in its, cathode circuit, comprising resistors 42, 30 and meter 3.1, to enable the meter to perform its function as an altitude indicator. The output voltage between the junction of resistors 42, 30 and ground, which voltage is proportional to altitude and results from the aforementioned flow of current, is applied to the input circuit of the servo controller and motor unit 14, by direct couping to resistors 45 and 46 (1 megohm and 250,000 ohms, respectively).

Reference is made to FIG. 1 in describing the broad principle applied in utilizing the altimeter output voltage to set the altitude knob or dial of bombsight 12. Those elements of FIG. 1 which are identical to the elements symbolically illustrated in FIG. 2 have the same reference numerals. The altitude voltage (V appearing across resistor 46 is applied to the input circuit of a servo controller 14a (comprising all components of unit 14 with the exception of servo motor 48 and its mechanical couplings to bombsight 12 and sliding contact 50). The servo controller amplifies the i nPut voltage applied thereto and applies the resultant output voltage to a servo motor 48. Motor 48 is mechanically coupled to a sliding contact 50 of a potentiometer 49, the potentiometer being coupled to a suitable potential source 52. The system is so arranged that upon application of V motor 48 runs and displaces the sliding contact until the position of the latter is such that the voltage (V acrossportion 53 of potentiometer 49 is equal to that across resistor 46. For this purpose, the output shaft of motor 48 is coupled to the slider by any suitable system of gearing and shafting indicated symbolically at 5 1 (1200zl reduction). The voltage across resistor 53 is also applied to servo controller 14:: with opposite polarity toythe first-mentioned controller input voltage from resistor 46. At "a time when the two voltages are equal and opposite no resultant input signal is appliedto controller 14a and servo motor 48"stops system balance then being restored.

Motor 48 is also coupled to altitude knob 13 of bombsight 12 by any suitable system of gearing and shafting indicated generally at 55. As altitude increases and voltage V increases the motor runs in such a direction as to increase the altitude setting of knob 13. For this condition V also increases. As altitude decreases and V decreases, motor 48 runs in such a direction as to cause V to decrease and to decrease the altitude setting of knob 13. When system balance exists, the alti tude setting of knob 13 is established by V The FIG. 1 system is restored to balance and the servo motor stops when V V =0. Referring now specifically to FIG. 2 of the drawings, it will be noted that V is applied between the control electrode 56 and the cathode 57 of a triode tube 58 (6SF5), the junctionofmesistorsjin 46 being connected to control electrode 56, and the grounded terminal of resistor-46 beingserialy included in a circuit comprising various resistors and terminating at cathode 57. Tube 58 is coupled to a double-triode tube 60 (6SN7) in such a manner as to disturb the balanced condition of equality between the anode voltages of tube 60 when the bias between elotrodes 56 and 57 of tube 58 departs from a predetermined value V The balanced condition of unit 14 therefore exists when V V =V When this balanced condition is disturbed, the appropriate one of relays 62, 63 becomes operative, closing an energizing circuit to the armature of motor 48. The motor makes the proper bombsight altitude adjustment and positions slider 50 insucha way as to equate V +V to V thereby restoring the pregletermined bias V between electrodes 56 and 57 of tube 8. The anodes of tube 60 are supplied with plate poten tial by a conventional vibrator power supply 64 having an output terminal 65 (+B) and a grounded terminal 66, connection being made from terminal 65 through variable resistor 67 (5000 ohms) to the junction of retion is performed by motor 48 in positioning slidingcon tact50. T

Since the curve illustrated in FIG. ;3' is not precisely linear, some form of equalizer must be inserted in" order to insure a linear output of tube 60; This is accomplished by shunting servo potentiometer '49 by resistor 77. This form of network gives to the follow-up voltage actuating the appropriate one of relays 62, 63 similar to the altimeter output voltage. Withinthe'v accuracy of the servo motor 48 no nonlinearity of motor output rotation with altitude is detected in practice;

Since an increase in altitude is accompanied by an in crease in V appearing across resistor 46, unit 14 is so arranged that sliding contact 50 is moved in such a direction (assumed to be counterclockwise) as to increase the length of portion 53 and therefore to increase the positive voltage V applied to cathode 57 of tube 58 sisters 69 and 70 (40,000 ohms and 6000 ohms, re-

spectively). The plate circuit of one triode of tube '60 comprises resistor 69, anode 71 and cathode 72. The plate circuit of the other triode of tube 60 comprises resistor 70, anode 73 and cathode 74. Cathodes 72 and 74 are effectively coupled to terminal 66 of power supply 5 64 by a circuit comprising resistor 75 (50,000 ohms), variable resistor 76 (100,000 ohms), a parallel combination of resistor 77 (500 ohms) and potentiometer 49 (20,000 ohms resistor 79 (1500 ohms), variable resistor 80 (2000 ohms) and grounded terminal 81 of resistor 46.

The potential between terminal 65 of power supply 64 and grounded terminal 81 is stabilized by a series combination of the following components: voltage regulating tube 83 (VRl05), voltage regulating tube 84 (VR75), voltage regulating tube 85 (VRlSO), and variable resistor 67. It will be seen that the voltage between ground and that the terminal of resistor 75 which is connected to cathodes 72 and 74 is stabilized by'regulator 83, so that the series combination of resistors 75, 76, 77-49, 79 and 80 comprises a constant-voltage source, corresponding to source 52 in FIG. 1, from which the voltages V and V are obtained. V ==V +V when the FIG. 2 system is in balance. The sum voltage of V +V required to satisfy this equation and to obtain a balanced condition of unit 14 is obtained by positioning sliding contact 50 on potentiometer 49 in an appropriate manner, since that sum voltage is made up of the voltages existing in portion 53 of potentiometer 49, resistor 79 and resistor 80. It has been seen that the voltage V appears across resistor 46, the only remaining circuit element between control electrode 56 and cathode 57 of tube 58. Thus voltage representative of the quantities to be equated are introduced in circuit between electrodes 56 and 57 and the equating opera- Attention is invited to theiactihralwr senrce.' a resnlt ei thisnoperation. thefiIm U-( o until the equation, VA =V VGI is sati'siedi fionvenseiy .Jhen altitude decreases slider 50 moves in the opposite (clockwise) direction until the equation is satisfied; Tiefore application of the altitude voltageV to unit 14, a predetermined bias voltage V (0.75 volt) is established for tube 58 and for this bias a predetermined voltage (6 volts) appears between'control electrode 89 and cathode 72 of double-triode tube 60; Voltage regulating tube 84 is connected between the junction offcathodes 72, 74 and control electrode 89 of tube 60, in series with a, resistor 94 (500,000 ohms) in order to provide this constant predetermined bias for electrode 89. For this operating condition, the voltage difierence between the plates of tube 60 is zero and thereforeno current flows through relays 62 and 63. An increase ordecrease in the bias voltage across resistor 94, due to a changeiu the bias on tube 58, causes either one relay or the other to operate, with the ultimate result that slider 50 is driven 'in such a direction as to bring the bias voltage of tube 58 back to the predetermined value (0.75 volt).

Anodes 71 and 73 of tube 60 are by-passed to' ground through condensers 91 and 92' (each 1 microfarad). A condenser 95 (8 microfarads) is connected to the junction of tubes 83-84 and by-passes cathodes72 and 74 to ground. In parallel with the series combination of resistors 69 and 70 are two relay circuits comprising: the series combination of solenoid 97 of relay 62, and one anode and cathode of a double-diode tube 99; and the series combination of solenoid 98 of relay 63 and the remaining cathode and anode of tube 99 (6H6); In shunt across the three series combinations is a series combination of a resistor 100 and a variable resistor 101 (the two having a'maximum value of, say, 100,000 ohms), for adjusting the relays with respect to sensitivity.

When relay 62 is energized it attractscontact member 103 to contact 104, attracts contact member 109 to con-v tact 110, and closes the circuit from a direct current power source, through conductor 105, terminal 1060f power supply 64, contact 104, contact member 103, mating terminals 7, 7 of connector 107, the armature of motor 48, mat ing terminals 4, ,4 of connector 107, contact108 audconjtact member 109 and contact110, mating'terminals 5, 5 of connector 107, switch 112, conductor 113, mating terminals 8, 8 of connector 107, ground, terminal 66 and grounded conductor 115 returning to the direct current motor 48 is excited and current flows therethrough in one direction. The motor then rotates in the appropriate direction. On the other hand, when solenoid 98 is energized so that relay 63 becomes operative contact member 109 is attracted to contact 116 and contact member 103 is attracted to contact 117, with the result that the, curlrent through the armature of motor 48 flows in the opposite direction and causes an oppositedirection of motor rotation. Specifically, the exciting current flows through conductor to terminal 106 of power supply 74, then through contact 116, contact member 109, contact 108, mating terminals 4, 4 of connector 107,'the

a variation very armature of motor 48, mating terminals 7, 7 of connector 107, contact 118, contact member 103, contact 117, mating terminals 6, 6 of connector 107, switch 119, conductor L13, mating terminals 8-8 of connector 107, ground, terminal 66 of power supply 64, and grounded conductor 115 of the direct current source. Thus it will be seen that the direction of rotation of motor 48 depends upon which one of relays 62 or 63 is energized. The latter condition is determined by the relative voltages of anodes 71, 73, of tube 60.

The symbols 0, M and N are applied to the filament heating currents of tubes 58, 60, and 99, respectively. A current regulator or ballast tube 121 (6A5) is connected in series between +A terminal 106 of power supply 64 and ground, along with the filament of tube 60 and the parallel combination of the filaments of tube 58 and tube 99 in order to prevent drift of the heating currents of these tubes (600 milliamperes for tube 60 and 300 rnilliamperes for each of tubes 99 and 58).

. The output of the power supply 64 is by-passed to ground by a condenser 122 (8 microfarads). An appropriate direct current potential source (not shown) is connected to conductors "1G5 and 115. Motor 48- is of the permanent magnet type, having a magnet 123 for providing the required magnetic field flux.

, Considering now the operation of the unit 14 just described, it will be assumed that the altitude of the craft is increasing and that V is increasing. Under that assumed condition, control electrode 56 of tube 58 becomes more positive and anode 87 becomes less positive. The bias across resistor 94 becomes more negative and the potential of anode 71 of tube 60 becomes greater than that of anode 73. The left-hand portion of tube 99 illustrated in FIG. 2. becomes conductive and relay 62 is energized. The circuit from conductors 105 and 115 to the armature of motor 48 is completed, due to operation of this relay, and motor 48 moves in such a direction as to cause an increase in the sum of V and V by lengthening portion 53 of potentiometer 49, while at the same time transmitting its motion to altitude knob 13 of bombsight 12 and setting in the correct altitude adjustment for the latter. This operation continues until slider 50 reaches such a position that the sum of the voltages between electrodes 56 and 57 of tube 58 attains the predetermined value (0.75 volt). As this value is approached the bias across resistor 94- becomes less negative and the potential of anode 71 approaches that of anode 73. When these potentials become substantially equal relay 62 is deenergized and motor 48 stops. By adjustment of resistor 101 the opening of the relay may be advanced, to

compensate for the efiects of inertia in delaying the stopping of motor 48.

Under conditions of decreasing altitude, the sum of V and V is initially greater than V control electrode 56 becomes less positive, anode 87 becomes more positive, the bias across resistor 94 becomes less negative, the potential of anode 71 becomes less positive than that of anode 73, relay 63 is energized, and the direction of motor operation is the opposite to that just described.

Mating terminals 1-1 of connector 107 are included in circuit with one terminal of resistor 49; mating terminals 2-2 are included in circuit with slider 50 and mating terminals 3--3 are connected in circuit with the remaining terminal of potentiometer 49. Further, when the system is in balance, contact members 103 and 109 are open-circuited and no current flows in the armature of motor 48.

The amount of rotation of sliding contact 50 for any specific increment of V is adjusted by means of calibration spread control comprising variable resistor 76. The positioning of the slider on the potentiometer is determined by the voltage from the low potential end of the potentiometer to ground. This is adjustable, the adjustment being accomplished by a calibration shift control comprising variable resistor 89. By adjustment of 8 the calibration shift control the position at which slider 50 comes to rest when servo unit 14 is in a balanced condition at a particular altitude is detennined.- By adjustment of the calibration spread control 76, the magnitude of the movement of slider 50 for any specific increment of V or change of altitude is'controlled.

While there has been shown and described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the true scope of the invention. For example, any conventional electronic altimeter having an appropriate output voltage characteristic may be substituted for the particular altimeter shown. Moreover, motor 48, mechanical couplings 51 and 55, potentiometer 49, and the associated portion of connector 1ii7 may be included in the bombrsight unit 12 as a matter of designers choice. It is, accordingly, intended in the appended claims to cover all such modifications and changes as fall Within the true scope of the inventionand without that of the prior-art.

I claim:

l. A servo controller responsive to an applied voltage of varying magnitude and a reversible servo motor having a movable member, said servo controller comprising a vacuum tube having an anode, a cathode and a control electrode, said control electrode being adapted to be connected to a source of the aforesaid applied voltage of varying magnitude, means varying the voltageof the cathode, a source of electrical current, a resistance connected between said source and said anode of the tube, a source of energy for said motor, means regulating said source to operate the motor either in a first direction or in a reverse direction, said movable member of the motor being coupled to the means for varying the voltage of the cathode, means producing a unidirectional reference potential of constant magnitude, and means including means responsive to changes inthe voltage of the said anode for comparing the said voltage changes with the said reference potential to produce a control signal for actuating said regulating means so that the voltage of the anode is maintained substantially equal to the said reference potential, and whereby the position of the movable member is a function of the applied voltage.

2. A servo controller responsive to a voltage of varying magnitude and a reversible servo motor having a rotor, said servo controller comprising a vacuum tube having an anode, a cathode and a control electrode, said control electrode being adapted to be connected to a source of the aforesaid voltage of varying magnitude, a potentiometer having a sliding contact, the contact being connected to the cathode of the vacuum tube to vary its voltage, a source of electric current, a resistance connecting said source to said anode to produce a 'unidirectional output potential, the rotor of said servo motor being coupled mechanically to the sliding contact,'means for energizing the servo motor, two relay means forcontrolling said energizing means to drive the rotor in one direction or the other, means including means for producing a unidirectional reference potential of constant magnitude coupled electrically to said anode for comparing the said output and reference potentialsto produce a control current for actuating one or the other of said relay means, whereby the rotor of said servo motor is operated to vary the voltage on the cathode of the vacuum tube in' the directionand to the extent required to maintain the said output and reference potentials substantially equal in magnitude, and whereby the angular displacement of the rotor is a function of the magnitude of the variable magnitude voltage applied to the control electrode of the vacuum tube.

3. A servo controller responsiveto an impressed D.C. voltage of varying magnitudes and a reversible rotor, said controller comprising a potentiometer for producing a DC voltage, and means comparing said impressed voltage with the voltage from the potentiometer and producing a voltage which is a function of the difference between said voltages, and means responsive to the voltage produced by said comparing means for controlling said motor, said means comprising two electron tubes each having an anode, a cathode and a control electrode, said tubes having their cathodes connected together, an electrical current supply means, anode circuit meansconnecting the anodes of the electron tubes to said current supply means, the control electrode of the first electron tube being connected to said comparing means whereby the voltage produced by said comparing means is impressed on said control electrode, the control electrode of the second electron tube being connected to its cathode, the parameters of said anode circuit being such that no potential difierence exists between the anodes of said electron tubes for a predetermined output voltage from said comparing means, two diodes connected in parallel between the anodes of said electron tubes, the cathode of one of said diodes and the anode of the other of said diodes being connected to the anode of the first electron tube, solenoids connected in series with said diodes, said reversible motor including a rotor, said rotor being coupled to said potentiometer, plural circuit means including said electric current supply means and a plurality of switch means connected to said reversible motor, said circuit means being so arranged that when one of the switch means is acuated to close a circuit means the rotor revolves in one direction, and when another switch means is actuated to close another circuit means the rotor revolves in the other direction, said switch means being actuated by said solenoids, whereby the voltage from the potentiometer is varied so as to restore the output voltage of said comparing means to said predetermined value, and the angular displacement of the rotor is a function of the magnitude of the impressed voltage.

4. A control system responsive to a voltage of varying magnitudes comprising a vacuum tube having anode, a cathode and a control electrode, said control electrode being adapted to be connected to a source of varying voltage, a potentiometer having a sliding contact connected to the cathode, a reversible electric motor including a rotor coupled to said contact for moving the contact and thus varying the potential of the cathode. electrical current supply means, a resistance connecting said anode to said electrical current supply means, a pair ot electron tubes each having an anode, a cathode and a control electrode, said tubes having their cathodes connected together, anode circuit means connecting the anodes of the electron tubes to said electrical current supply means at a common point, the control electrode of the first of said electron tubes being connected to the anode of said vacuum tube, whereby a predetermined bias is applied thereto. the control electrode of the second electron tube being connected to its cathode, the

' wnenone 'ot'the switeh meansisactuated tccccmpletein parameters of the anode circuits of said electron tubes 7 being such that no potential difierence exists between the anodes of said electron tubes when said predetermined bias exists on the control electrode of the first 10 electron tube, two diodes connected in parallel between the anodes of said electron tubes, the cathode of one of said diodes and the anode of the other of said diodes being connected to the anode of the first electron tube, solenoids connected in series with said diodes, plural circuit means including said electric current supply means and switch means connected to said reversible electric motor, said clrcurt means being so arranged that first circuit, the motor revolves in one direction, and when the other switch means is actuated to complete a second circuit, the motor revolves in the other direction, said switch means being actuated by the solenoids, whereby, when the difierence in voltage between the control electrode and the cathode of the vacuum tube difiers from a predetermined amount, the motor means are actuated to vary the voltage of the cathode of the vacuum tube so that the predetermined difierence in voltage is restored, whereby the angular displacement of the rotor is a function of the magnitude of the voltage applied to the control electrode of said vacuum tube.

5. A closed loop servo controller comprising: an ele-' ment to be controlled; means for producing a first unidirectional potential having a magnitude representing a first quantity; means coupled to the said element for producing a second unidirectional potential having a magnitude representing the instantaneous condition of the said element; means responsive to the said first and second potentials for developing a unidirectional error potential having a magnitude representing the instantaneous difierence between the said first quantity and the condition of the said element; means for producing a unidirectional reference potential of predetermined magnitude; means for comparing the said error potential and the said reference potential to produce a control current having a direction and magnitude representing the direction and magnitude of deviation of the said errer'potential'fremthe saidreterencctnoient g a 1116,3115

responsive to the said control current for causing the Instantaneous condition of the said element to be controlled to be established in accordance with the said first quantity, thereby tending to produce equality between the said error and reference potentials.

6. A closed loop servo controller as represented in claim 5 wherein a source of regulated direct-current sup ply potential is coupled to the said condition-producing means, the said error-potential developing means, the said reference-potential producing means, and the said comparing means.

References Cited in the file of this patent UNITED STATES PATENTS 1,914,481 Brown June 20, 1933 2,113,436 Williams Apr. 5, 1938 2,203,689 McDonald June 11, 1940 2,363,473 Ryder Nov. 21, 1944 FOREIGN PATENTS 976,498 France Dec. 15, 1948 

